Today, the mobile industry is moving towards using the power sources with potentially unreliable or fluctuating and time dependent power capabilities. These sources include wireless power, solar power, as well as Universal Serial Bus (USB) Power Delivery (PD) power supplies. Also, there is continued drive for higher relative turbo power by System-on-a-Chips (SoCs) and other integrated circuits used in computing systems. Even while this occurs, there are still demands for smaller adapter sizes.
More specifically, with respect to wireless energy, one of the issues that worries power delivery engineers is the fact that the amount of power transmitted from the power source to the charger of the mobile device varies dependent on the distance from the power source and the receiver, the device orientation and the like. With respect to solar panels, the energy that can be captured and converted to electrical energy is strongly dependent on the time of day, strength of solar radiation and the like. Thus, in both these cases, it may be unknown to a computing system being powered by such energy sources as to the amount of power that they may receive.
Some customers may also experience issues with USB adapters when the actual output power of the power adapter may not be necessarily known beforehand, or when a universal USB adapter is made by a second-tier supplier and may be designed for lower temperature or may even have less than required output power capability.
For all of the cases discussed above, the system being powered (i.e., the system load) will in some cases require too much power from the power source to support system operation and/or charge the battery, and a number of corner cases arise when the system does not know the actual maximum output power capability of the source. This include the situation of when the power adapter is designed for limited periods of peak power, but cannot handle longer duration high load. A real life situation would be for the power source to be periodically shut off because its power capability is exceeded, and the system may cut off a battery charger in the power system from the input power. The result of this corner case could be damage to the system circuitry or the power source, audio noise irritating to the end-users, as well as the system drawing less power from the power source than possible.